Lang graduated with high honors from Swarthmore College in 2003 with a degree in Political Science and History and a concentration in Interpretation Theory.

[citation needed] In 2006, Lang began her career as an Assistant DA in Manhattan under District Attorney Robert M. Morgenthau, first in the Appeals Bureau and later in the Trial Division.

Under DA Cyrus R. Vance, Jr., she served as Special Counsel to the District Attorney as well as executive director of the in-house think tank, the Manhattan D.A.

[10][11] Lang became the executive director of the Institute for Innovation in Prosecution in 2018,[12] working with prosecutors and communities to promote safety, fairness, and dignity in the criminal legal system.

[16][17][18][19] In August 2020, Lang began her campaign for Manhattan District Attorney, citing the impact of the coronavirus in New York and protests against police brutality sparked by the murder of George Floyd as motivating factors in her decision to enter the race.

[24][25] Lang has been endorsed by progressive prosecutors from across the country, including Marilyn Mosby, Sherry Boston, Sarah Fair George, John Choi, Kimberly Gardner, and Scott Colom.